Exam 3

Question 1

What is one example of isozyme regulation of glycolysis?

a. Pyruvate kinase is allosterically inhibited by ATP, slowing glycolysis.
b. Hexokinase IV is not inhibited by glucose 6-phosphate.
c. PFK phosphorylates carbon 2 rather than carbon 1, creating fructose 2,6-bisphosphate.
d. Pyruvate kinase is not inhibited by glucose 6-phosphate.

Answer 1

b. Hexokinase IV is not inhibited by glucose 6-phosphate.

Note: Hexokinase IV isozyme, aka “glucokinase” is not allosterically inhibited by its product glucose 6-phosphate (feedback inhibition is does not occur). Its Km for glucose is 100x higher than the other hexokinase isozymes, meaning it can only phosphorylate glucose if the concentration of substrate is high enough. It plays an important regulatory role in carbohydrate metabolism i.e. a glucose sensor to control insulin release.

Question 2

Which of the following statements about GLUT transporters is NOT true?

a. GLUT 2 has a high affinity for glucose and is always active.
b. GLUT 5 can transport fructose and is regulated by cytokines.
c. GLUT 1 has a high affinity for glucose when activated.
d. GLUT 4 has a low affinity for glucose and is found in cells that produce insulin.

Answer 2

a. GLUT 2 has a high affinity for glucose and is always active.

Note: GLUT 2 has a LOW affinity for glucose and it is always active. GLUT 2-4 are found in cells that can sense levels of glucose and produce/release insulin accordingly.

Question 3

GLUT5 Transporter

Answer 3

• Can transport fructose
• Regulated by cytokines

Question 4

GLUT1 Transporter

Answer 4

• Very high affinity for glucose when activated
• Regulated by insulin

Question 5

GLUT2-4

Answer 5

• Lower affinity for glucose (always active)**
• Found in cells that can sense levels of glucose and produce/release insulin accordingly (i.e. ß-cells of the pancreas)

Question 6

Production of Insulin

Answer 6

ß-Cells of the Pancreas:

• GLUT2 transports glucose into the cell
  
  • increased production of ATP (glycolysis)
• ATP causes allosteric inhibiton of K⁺ channels
• Voltage gated Ca²⁺ channels open
  
  • Ca²⁺ binds to insulin vessicle
  • Insulin vessicle fuses with cell wall
• Release of Insulin into blood vessels

Question 7

Which Process Occurs first in the Embden-MeyerHof Pathway?

a. Substrate level Phosphorylation via. 1,3-Bisphosphoglycerate (BPG)
b. 1-6, Biphosphate is split by Aldolase
c. Glucose 6-Phosphate is converted to Fructose 6-Phosphate
d. Substrate level Phosphorylation via. Phosphenylpyruvate

Answer 7

c. Glucose 6-Phosphate is converted to Fructose 6-Phosphate

Question 8

Which of the following statements is true regarding the processes involved in the Embden-MeyerHof Pathway?

a. The pathway produces a net gain of 4 ATP
b. Phosphoglucose Isomerase catalyzes a Ketose®Aldose reaction
c. Hexokinase is directly inhibited by Glyceraldehyde 3-Phosphate (GAP)
d. Oxidation of GAP gives 1,3-Bisphosphoglycerate (BPG) high phosphoryl transfer potential.

Answer 8

d. Oxidation of GAP gives 1,3-Bisphosphoglycerate (BPG) high phosphoryl transfer potential.

Question 9

Histones are largely involved in what type of reaction?

a. Phosphorylation
b. Redox
c. Isomerization
d. Acetylation

Answer 9

d. Acetylation

Question 10

Which of the following is NOT true of ATCase?

a. ATCase displays sigmoidal kinetics.
b. ATCase is composed of discrete catalytic and regulatory subunits.
c. ATCase exists only in the T-state.
d. ATCase favors CTP binding while in the T-state.

Answer 10

c. ATCase exists only in the T-state.

Question 11

If a muscle fiber contracts, which of the following may occur in glycolysis?

a. Fructose 1,6-bisphophate signals pyruvate kinase production
b. ATP phosphorylates pyruvate kinase
c. AMP binds to pyruvate kinase
d. ATP binds to PFK

Answer 11

a. Fructose 1,6-bisphophate signals pyruvate kinase production

Question 12

If a muscle fiber was in a relaxed state, which of the following molecules may interact with PFK?

a. AMP
b. Glucose 6-phosphate
c. Fructose 1,6-Biphosphate
d. ATP

Answer 12

d. ATP

Question 13

What is something critical to having structural components in connective tissue and mediating adhesion of cells to the extracellular matrix?

a. Proteoglycans
b. Unglycosylated Proteins
c. 1,3-Glucosulfuric Bonds
d. Polygalacturonic Acid

Answer 13

a. Proteoglycans

Question 14

How might a mutation in the Golgi complex effect glycosylation?

a. N-linked glycosylation would not happen
b. O-linked glycosylation would not happen
c. Formation of Dermatan Sulfate would not occur
d. Protein production would not be affected

Answer 14

b. O-linked glycosylation would not happen

Question 15

In a situation where energy is needed…

a. AMP concentration is low, stimulating phosphofructokinase.
b. AMP concentration is high, stimulating phosphofructokinase.
c. AMP concentration is high, stimulating fructose 1,6-bisphosphatase.
d. ATP concentration is high, stimulating fructose 1,6-bisphosphatase

Answer 15

b. AMP concentration is high, stimulating phosphofructokinase.

Question 16

What makes enzyme activity dynamic or responsive in the cell?

a. increased concentration of enzyme or substrate
b. decreased quantity of enzyme or substrate
c. having an enzymes activity not dependent on substrate concentration
d. allowing for no degradation of the enzyme

Answer 16

a. increased concentration of enzyme or substrate

Question 17

Which is not a reason that there are clusters of hydrophobic residues in Glut 1?

a. Hydrophobic regions span the membrane of Glut 1
b. There are membrane spanning alpha helices that may open or close membranes
c. Glut 1 contains beta barrels
d. Glut 1 is made up of beta sheets that prevent water from binding to Glut 1

Answer 17

d. Glut 1 is made up of beta sheets that prevent water from binding to Glut 1

Question 18

Which of the following is NOT a source for gluconeogenesis to occur?

a. Lactate
b. Amino acids
c. Glycerol
d. Insulin

Answer 18

d. Insulin

Question 19

Which pathway(s) does Fructose-1,6-Bisphosphatase belong to?

Answer 19

Gluconeogenesis

Question 20

Glycoproteins are unique molecules that are essential to many metabolic processes in many organisms. Within these molecules, sugars are attached to “linker” residues within the protein to form the glycoprotein. Which of the following residues would we most likely expect to be bound to the sugar within a glycoprotein?

a. Serine
b. Glycine
c. Lysine
d. Tryptophan

Answer 20

a. Serine

Question 21

Which of the following residues are likely to be involved in interactions with peripheral membrane proteins?

a. Tryptophan
b. Threonine
c. Cysteine
d. Phenylalanine

Answer 21

b. Threonine

Note: it is the only polar residue listed. The other polar amino acids include serine, tyrosine, asparagine, glutamine, and cysteine.

Question 22

Rigor mortis, a recognizable sign of death, is the stiffness observed in the muscle within hours after an individual passes away. What is the biological cause of rigor mortis?

a. The exhaustion of glucose.
b. The body no longer produces ATP.
c. The increased production of ADP.
d. The depletion of glycogen.
e. Both a and b.
f. Both b and d.
g. Both a and c.

Answer 22

f. Both b and d.

Question 23

Why does inhibition of phosphofructokinase (PFK) lead to inhibition of hexokinase?

a. Due to a buildup of AMP
b. Due to a buildup of glucose 6-phosphate
c. Due to a decrease of ATP
d. Due to a buildup of fructose 6-phosphate
e. Both (b) and (d) are correct

Answer 23

e. Both (b) and (d) are correct

Question 24

During exercise, which is FALSE about glycolysis regulation?

a. A decrease in the ATP:AMP ratio stimulates phosphofructokinase activity.
b. Fructose 1,6-bisphosphate stimulates pyruvate kinase activity.
c. A decrease in pH stimulates phosphofructokinase activity.
d. Glycogen can be broken down to glucose 6-phosphate.

Answer 24

c. A decrease in pH stimulates phosphofructokinase activity.

Question 25

How does gene duplication lead to the development of Isozymes? a. One gene encodes for the T state and it's duplicate encodes for the R state b. Two copies of the gene that encodes for the enzyme allows for the one of the copies to be mutated prior to protein synthesis c. Two copies of the gene that encodes for the enzyme allows for the enzyme to mutate after protein synthesis d. Duplication of the gene that encodes for the enzyme allows for faster synthesis of the protein

Answer 25

b. Two copies of the gene that encodes for the enzyme allows for the one of the copies to be mutated prior to protein synthesis

Question 26

The standard free energy of hydrolysis for ATP is -30.5 kJ mol-1 ATP + H20 → ADP + Pi What conditions might be changed to alter the free energy of hydrolysis? (more than one may be correct) a. Increasing the concentration of ATP b. Decreasing the concentration of cellular ADP or Pi c. Decreasing the concentration of ATP d. Increasing the concentration of cellular ADP or Pi

Answer 26

(a) and (b) are correct ## Footnote a. Increasing the concentration of ATP b. Decreasing the concentration of cellular ADP or Pi

Question 27

How might the enzymes that remove amino groups from alanine and aspartate contribute to gluconeogenesis? a. Pyruvate and oxaloacetate are formed- both part of the gluconeogenesis pathway b. Helps speed up the reaction c. The ring created from the removal is glucose d. Helps to break down lactic acid using the products formed

Answer 27

a. Pyruvate and oxaloacetate are formed- both part of the gluconeogenesis pathway

Question 28

The process of phosphorylating a sugar is done to change the structural and behavioral characteristics of the molecule in several ways, one of these being that the addition of a phosphate group makes the molecule anionic and prevents it from spontaneously leaving the cell. What is another reason for this process? a. Increase the reactivity of the molecule with the phospholipid membrane b. Prevents interaction with transporters of unmodified sugars c. To increase the rate of metabolizing the sugar d. To increase the likelihood of bonding with other sugars

Answer 28

b. Prevents interaction with transporters of unmodified sugars

Question 29

The process of glycolysis can be done through utilizing and breaking down glucose, as well as amino acids, lipids, and stored glycogen. Why then is glucose the preferred molecule to metabolize over the other three? a. Using glucose results in much more ATP being produced b. Using amino acids, lipids, or glycogen negatively affects other body functions c. Glucose does not require structural change before metabolism d. Using glucose diminishes the fat reserves of the body

Answer 29

c. Glucose does not require structural change before metabolism